Gonotrophic development and survival in field populations of Musca domestica (Diptera: Muscidae) at dairies in California, Minnesota, and Georgia, and the relationship of fly age to relative abundance of (Z)-9-tricosene (muscalure).

Adult female Musca domestica L. were collected in 2004 and 2005 from dairies in California, Minnesota, and Georgia. Relative abundance of (Z)-9-tricosene (muscalure) among the dominant eight hydrocarbons was determined. Fly heads then were removed to quantify pterin levels and estimate fly age, abdomens were dissected to score gonotrophic development and parity (follicular relics), and spermathecae were examined for sperm. Daily survival was assessed using two estimates of time required to become gravid: laboratory-based degree-day (DD) estimates and estimates based on pterin values in field-collected flies matched to their stages of gonotrophic development. Among newly emerged females (oocyte stage 1) with detectable muscalure, it comprised < approximately 1.5% of cuticular hydrocarbons. In muscalure-positive flies, muscalure comprised a higher proportion of cuticular hydrocarbons in older flies from California and Minnesota (6-9% when gravid) versus flies from Georgia (<2% when gravid). Females mated in early-intermediate stages of egg development. Life expectancy, using laboratory-derived estimates of time needed to become gravid, ranged from 3.6 to 10.6 d. Using equivalent pterin-based time estimates, life expectancy ranged from 4.0 to 19.5 d. Mean DD ages (12 degrees C threshold) of gravid flies varied widely (53-95 DD) and were congruent with laboratory-based estimates (52-57 DD) in only 7 of 12 farm-year combinations. Thus, house flies under natural conditions often required more time to develop eggs than laboratory models would predict, extending daily survival estimates based on gonotrophic age by 11-74%.